Endohedral metallofullerenes are spherical fullerene carbon cages confining one or more metal atoms in their interior spaces. Biomedical applications exploiting special properties of metallofullerenes in different areas are promising, including diagnostic and imaging agents (magnetic resonance imaging (MRI) contrast agents, X-ray contrast agents, radiotracers), therapeutic nuclear medicine, antioxidants and biosensors. In our development of Gd-containing endohedral metallofullerenes as paramagentic MRI contrast agents, we have recognized the need for expanding the available raw materials beyond just the soluble Gd@C82 metallofullerenes, which comprise only about 4% of the sublimable Gd metallofullerenes produced by the carbon arc process. We propose to combine new advances in the areas of metallofullerene production and post-production processing to both increase the yield of generated metallofullerenes and to separate and purify the large majority of Gd endohedrals that the current processes can not access. Separative processing based on a chemical redox strategy will allow us to utilize all of the available Gd metallofullerenes by differentiating them into different classes based on their physical and chemical properties. Careful analytical evaluation of the obtained Gd metallofullerene fractions will be performed, allowing evaluation and comparison to other processes for the first time. These advances will benefit the development of MRI contrast applications with metallofullerenes by creating means to generate more raw material while separating the mixture of produced metallofullerenes into useful, homogeneous fractions. In summary, this project will improve processes for manufacture and purification of new materials that are the main ingredient in a new type of useful drug. These can help improve MRI scans used for detecting diseases and are also potentially useful for other medical treatments and applications.